In the last decade, the cases of women who have given birth to twins or even triplets have increased, which has led infertility specialists to establish a series of guidelines to prevent this, since multiple pregnancies entail more risks than singleton pregnancies.
Being pregnant with more than one embryo can lead to severe complications for both the health of the mother and the babies. For these reasons, carefully evaluating the pros and cons before making a decision as regards the number of embryos to transfer.
The different sections of this article have been assembled into the following table of contents.
Fraternal vs. identical twins in ART
Multiple pregnancies achieved following assisted conception result in fraternal twins and not in identical twins, since they are the result of two eggs that have been fertilized using two different sperms.
This occurs because ovarian stimulation, both in Intrauterine Insemination (IUI) or In Vitro Fertilization (IVF) cycles, triggers the maturation of multiple follicles, each one containing a different egg.
The chances of getting pregnant with twins are higher in IVF cycles where multiple embryos are transferred. For this reason, the general recommendation is to transfer a single embryo in all cases. Nonetheless, in certain cases such as women of advanced maternal age, the specialist may consider transferring two or more embryos.
Based on the data generated by all clinics providing ART services, the American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) have defined a series of guidelines to follow when it comes to deciding the number of embryos to transfer:
Patients under the age of 35 should be encouraged to receive a single-embryo transfer, regardless of the embryo stage. For patients between 38 and 40 years of age, no more than three cleavage-stage embryos or two blastocysts should be transferred. Patients 41–42 years of age should plan to receive no more than four cleavage-stage embryos or three blastocysts.
In Intrauterine Insemination (IUI) cycles, mild ovarian stimulation is performed in order to trigger the development of a maximum of one or two follicles, so that finally only one egg is fertilized. In case multiple follicles develop, the cycle should be cancelled to avoid a multiple pregnancy.
One should not forget that a twin pregnancy can occur naturally, even if pregnancy is achieved through ART. The embryo can split into two after insemination or IVF embryo transfer, resulting in identical twins.
Seeking IVF to have twins
Nowadays, reproductive endocrinologists and & infertility specialists insist on the importance of elective single embryo transfers (eSETs) to prevent a multiple pregnancy. However, many patients disagree with this.
Most intended parents do not want to stack everything on a single embryo. In fact, they prefer to have fraternal twins from a single cycle in order not to go through another cycle in the future to have more children.
If you need to undergo IVF to become a mother, we recommend that you generate your Fertility Report now. In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.
Fertility treatments are hard to cope with emotionally. Several regular visits to the clinic, along with the expensive cost of fertility treatments per cycle, make them inaccessible for many families.
The following are the main pros and cons of getting pregnant with multiples following ART:
Pros of multiple pregnancies
As we have explained above, the main advantage of a multiple pregnancy following ART is that the couple does not need to start a cycle anew. With the birth of two babies at the same time, they fulfill their dream of becoming parents and stop seeking a new pregnancy.
Another advantage is that, when pregnant with twins, the intended mother goes through pregnancy and childbirth only once, experiences that only few women are willing to repeat over their lifetime.
Finally, we should mention the special bond that develops between twins. They grow up together, learning to share everything with each other, and become excellent playmates.
Cons of multiple pregnancies
The main cons of multiple pregnancies are due to the risks it conveys for both the mother and the babies, including:
- Preterm birth
- When delivery occurs before week 37 of pregnancy.
- Placenta previa
- When the placenta attaches near to the cervix, covering it totally or partially.
- A type of high blood pressure that occurs during pregnancy. It causes kidney problems, causing the loss of proteins through urine.
- Gestational diabetes
- A type of diabetes that appears for the first time when the woman gets pregnant. It typically appears after the first trimester.
- C-section birth
- A surgical incision is performed on the abdomen and the uterus to deliver the babies.
- Postpartum bleeding
- It is considered bleeding if the loss excess more than 500 ml of blood after a vaginal birth, or over 1,000 after a C-section.
- Miscarriage or vanishing twin syndrome
- Although most twin pregnancies develop without problems, the risk of miscarriage is higher than in singleton pregnancies.
- Twin-to-twin transfusion syndrome
- A pregnancy complication that occurs when the fetuses share the same placenta, since blood is transferred between one another. A blood deficiency can occur in one of them, with the subsequent excess for the other.
- Intrauterine growth restriction
- The fetus is unable to grow as much as he needs due to a deficiency of nutrients and/or oxygen. Usually, it is due to complications in the placenta.
- Low birth weight
- It is diagnosed when the weight is below 2.5 grams.
- Perinatal mortality
- Perinatal death occurs when the fetus dies at week 28 of pregnancy or later, or within the first seven days after being born.
- Chromosomal abnormalities
- It is estimated that multiple pregnancies carry two times the risks of developing chromosomal abnormalities than singleton pregnancies, especially if the mother is 35 years old or more.
Furthermore, if the intended mother is older than 38, a multiple pregnancy can increase the risk for other complications, including thrombophilia or cardiac arrest. For this reason, if a multiple occurs from ART, sometimes doing a selective reduction is necessary in case 2 or more embryos have implanted.
On the other hand, once the babies are born, complications may arise at home. A greater volume of tasks to do, sleepless nights, money, etc. is required as the number of children increases. Twin children require their parents' full attention, and sometimes even extra help is necessary.
FAQs from users
Is a preterm birth more likely with twins?
According to the World Health Organization (WHO), a preterm birth occurs when the child is born before the week 37 of pregnancy. Some of the most common causes of preterm birth are:
- Overdistention of the uterus: loss of tone in the uterine musculature that prevents this organ to recover its normal size.
- Infection or uterine inflammation: certain bacteria can damage fetal membranes by causing its rupture and triggering a preterm birth. An infection that affects the uterus directly may lead to preterm birth as well.
- Decidual bleeding: a type of vaginal bleeding that may occur while a woman is pregnant.
There exist many risk factors that can lead to premature birth, including obesity, high blood pressure, etc. A multiple pregnancy is one of these factors.
How can multiple pregnancy from assisted reproductive technology be prevented?
There are lots of actions to be taken, most of them being implemented with increasing success.
As for in vitro fertilisation, a three-embryo transfer should be avoided: cases with a good prognosis should bet on a single embryo transfer instead. This requires a process of raising awareness not only by the couple undergoing the treatment but also by the professional team.
The “success” of an assisted reproductive treatment does not consist only on achieving pregnancy. More and more, we need to be aware that the ultimate aim should be having a healthy baby, that is to say, that the child is not born too early.
Despite changing this mindset may be difficult, we insist on the need to prevent multiple births.
I want to have twins. Can I make this decision in my IVF cycle?
Yes, it is possible for a woman or couple to decide to transfer two or more embryos instead of just one. However, you should follow strictly the recommendations of specialists and prevent the risks a multiple pregnancy entails. Moreover, not all embryos transferred are always able to attach to the uterus.
Can you get pregnant with twins after using donor eggs?
Yes, although it depends on the number of embryos transferred. Moreover, the pregnancy success rates with donor eggs are higher than with own eggs, given that donor eggs have an excellent quality.
Suggested for you
To get more info about the things to keep in mind when it comes to deciding how many embryos to transfer in an IVF cycle, click here: How Many Embryos Should You Transfer for IVF?
A multiple pregnancy entails several risks, especially in women of an advanced maternal age. Want to learn more about this? Read: Potential Complications of Multiple Pregnancies.
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FAQs from users: 'Is a preterm birth more likely with twins?', 'How can multiple pregnancy from assisted reproductive technology be prevented?', 'I want to have twins. Can I make this decision in my IVF cycle?' and 'Can you get pregnant with twins after using donor eggs?'.